The examination of mosquito larvae collected by house searchers on Stegomyia control measures in Dar-es-Salaam, the largest town in Tanganyika, shows that Aëdes aegypti is definitely the predominant domestic breeder there. The other species of the genus Aëdes encountered are listed with their frequencies.

Similarly the examination of larvae found in tree-holes in Dar-es-Salaam shows that Aëdes aegypti, A. simpsoni and A. metallicus are regularly encountered.

A system of obtaining an index of the population density of both A. aegypti and A. simpsoni, unconnected with the actual process of Stegomyia control measures, is described. This would be applicable to smaller towns, rural districts, and towns in high rainfall areas where A. aegypti is not the only danger as a yellow fever vector, and where extra-domestic breeding is important. The system is based on the exposure of a fixed number of bamboo pots containing water for a constant period of days, to attract egg-laying female mosquitos. Species of mosquitos and their frequencies obtained in a series of trials are given.

[A voluminous general report on the organisation and the results of the locust investigations carried out in India in 1931–1938, under the auspices of the Imperial Council of Agricultural Research, was officially submitted to the Council by Rao Bahadur Y. Ramchandra Rao in 1941, but its publication has been postponed until after the war.

A copy of the report has been sent, by permission of the Council, to the Anti-Locust Research Centre at the Imperial Institute of Entomology, for information, and it proved to contain a wealth of data and of ideas, only some of which have been published in various preliminary papers by its author and by his colleagues. In view of the great scientific and practical value of the report, it appeared necessary to make at least its main findings available to other entomologists working on the subject, and permission has been obtained from the author and from the Imperial Council of Agricultural Research for the publication of some sections of the report. Only a few sections, selected and edited by Dr. B. P. Uvarov, are being published below, and it should be stressed that their publication in the abridged form does not in any way detract from the value of the complete report, which, it is hoped, will be published at the earliest opportunity for the benefit of all workers on the locust problem.]

This Anopheline was first found in Syria in the larval stage on 30th August 1941. Up to the time of writing, 11th October 1941, adults and larvae have been taken on several occasions. Isolated larvae have been bred to the adult stage, and larval and pupal pelts preserved. Through the courtesy of Professor S. Adler and Dr. O. Theodor, of the Hebrew University at Jerusalem, I was able to consult the literature regarding the distribution of this species and to confirm its identification. The discovery of Anopheles marten in Syria is a new record.

The Sugar Industry of Mauritius is suffering heavily from damage by stem-borers, especially the “Spotted Borer,” Diatraea mauriciella, Wlk. It has been estimated (Moutia, 1934) that this species alone is responsible for an average reduction of 15 per cent, in the field, per arpent, and that the loss in sugar averages 2-3 per cent., i.e. 16 per cent, of the sugar in cane. This means a gross loss of about 1£ million rupees per annum for the whole island, or a net loss of approximately 125,000 rupees.

(1) Adult female Sarcoptes were killed by 49°C. (120°F.) in 10 minutes and by 47·5°C. (117·5°F.) in 30 minutes.

(2) At 28°C. (82°F.) no Sarcoptes survived for two days and the majority died in 24 hours.

(3) At 13°C. (55°F.) and 90 per cent. R.H. the majority of the mites died within a week, but a few survived longer, even up to 14 days.

(4) At temperatures below 13°C. (55°F.) the mites survived for a shorter time.

(5) Sarcoptes gives no reactions, positive or negative to unidirectional light.

(6) Below 15°C. (59°F.) Sarcoptes is in chill coma. Little movement occurs below 20°C. (68°F.).

(7) In temperature gradient mites seldom, if ever, go below 24°C. (75°F.). They will walk into high temperatures which prove rapidly lethal.

In practice it is seldom found that any one of the numerous grades of oil prepared from crude petroleum is a satisfactory mosquito larvicide. The final product is almost invariably blended from several constituents. Each of the constituents may confer beneficial properties on the larvicide directly, or it may serve to correct undesirable features possessed by the other ingredients.

Even under world conditions which might be regarded as normal compared with those prevailing to-day, difficulties have confronted those who wished to select or blend a larvicide. There was firstly, in the remoter parts of the world, a lack of any specialised chemical apparatus ; secondly, the lack of a complete minimum performance specification by which to judge laboratory blends ; and thirdly, the difficulty arising from the fact that the specifications supplied for commercial grades of oil do not include data on many properties of the oil which are important to the malariologist but unimportant to the usual consumer.

This paper represents an endeavour to overcome the three difficulties outlined above. It provides a minimum performance specification for a larvicide and describes a series of simple tests which may be applied (a) to a commercially blended larvicide in order to establish whether this meets the requirements of the specification, and (b) to the individual ingredients (e.g., kerosines, Diesel oils or fuel oils) so that, in each case, the one with the most desirable combination of properties may be selected for incorporation in the final blend.

The history of this insect is so involved that perhaps the simplest method of attempting to find out how to arrive at its correct name will be to start with a chronological list of the references involved.

Insects immersed in oils exude minute droplets of water over the surface of the cuticle. These appear more rapidly in light oils than in heavy oils and are more numerous in young insects than in old. Immersed in mixtures of oils and alcohols which separate in contact with water they show a vigorous effervescence at those regions where the mixture penetrates most rapidly to the water in the cuticle. There is a delay of varying duration at different parts of the cuticle when heavy oils are used. This delay disappears if the lipoid layer is first extracted with petroleum ether.

Factors controlling the rate of entry of pyrethrum through the cuticle have been studied by the application of pyrethrum in oil to a restricted area of the abdomen of nymphs and adults of Rhodnius. Entry is more rapid in light than in heavy petroleum oils ; it is much accelerated if the cuticle is first treated with petroleum ether. Entry is very slow in vegetable oils. There are great individual variations, due chiefly to the thickness of the endocuticle, which in turn is determined by the size of meal taken before moulting, the age and the amount of food taken after moulting, and the degree of stretching of the cuticle. There is evidence that the pore canals are important in the passage of pyrethrum through the endocuticle.

Histological examination of the integument shows that in the nymph of Rhodnius oils are taken up first by the epidermal cells in the zone around the bristles ; later by the general epidermis. The uptake of oil is greatly increased if 5 per cent. of oleic acid is added to refined petroleum. In the adult Rhodnius soon after moulting, oils are taken up by the general epidermis. In old insects they are taken up solely by the dermal glands. There is no visible entry through the sockets of the bristles.

The entry of pyrethrum in oils is accelerated by the addition of oleic or other fatty acids.

(1) Coal-tar phenols are useful intermediate solvents for making solutions of rotenone in both mineral and vegetable oils.

(2) Medium petroleum oil showed superiority to ground-nut oil as a carrier of rotenone in xylenol tested against Ornithodorus moubata.

(3) The solutions of rotenone in xylenol and oil showed no deterioration after storage in the dark at room temperature for six weeks.

(4) In these solutions rotenone proved far less toxic to Ornithodorus moubata than an equal weight of pyrethrin I in medium petroleum oil.